In the production of pharmaceutical dosage forms, the active ingredients are retained by inactive ingredients to facilitate the forming of a tablet or capsule that may be ingested and also to facilitate the metering of the dosage release. One aspect of dosage form development and quality control involves determining the release profile of the drug from the inactive carrier. The United States Pharmacopeia (USP) and the National Formulary have standards for testing the dissolution of the dosage form wherein the dosage form is placed in a fluid medium and the fluid is sampled at set intervals to determine the concentration of the active ingredient in the fluid.
Recently, modified release dosage forms based on gel formation have been developed. These dosage forms involve three dimensional swelling of the gel for subsequent drug release over periods of 1 to 24 hours. The gel-forming products acquire low density upon swelling and often float in the vessel when tested with standard dissolution test methods. To keep the object submerged, the USP recommends attaching a small loose piece of non-reactive material, such as a few turns of a wire helix. However, wire hinders the object's three-dimensional swelling in the fluid, thereby leading to release profiles with poor reproducibility. Moreover, some products contain three or more gel forming units enclosed within a capsule shell. Such products will not be retained with the wire helix once the gelatin shell is dissolved.
A dissolution testing method and apparatus is needed that does not add additional constraints to the dissolution of the dosage form.